This invention relates to a light deflecting device for use in a laser beam printer, a bar code reading apparatus or the like and a device for regulating such device.
Heretofore, in light deflecting devices for deflecting a light beam, rotational polygon mirrors rotatable in one direction have been widely used because of the stability of their speed of rotation and their scanning speed.
However, where such a rotational polygon mirror is used as the light deflecting device of a scanning optical apparatus, there is a problem that the deflecting-scanning surface or the reflecting surface thereof tilts from a plane perpendicular to the ideal main scanning surface to be formed by a scanning beam deflected thereby.
A means for solving such a problem is, for example, one as disclosed in Japanese Laid-Open Patent Application No. 63-188112 (corresponding U.S. Application Ser. No. 149,020 filed on Jan. 27, 1988 (now U.S. Pat. No. 4,915,465) and corresponding EP Application No. 88101263 filed on Jan. 28, 1988 and published on Aug. 17, 1988 under EP Publication No. 0278332). That is, the opposed portions of a cylindrical metallic member are cut into parallel flat surfaces and these two surfaces are used as reflecting surfaces for deflecting and scanning a light beam. This rotational mirror is mounted so that the two parallel reflecting surfaces may be parallel to the direction of inclination of the mounting flange surface of the rotational mirror and thereby the above-mentioned tilt of the reflecting surface of the rotational mirror by the inclination of the mounting flange surface may not occur, whereby the irregularity of the pitch of scanning lines on a surface scanned by a scanning beam may be minimized.
By this method, it is made unnecessary to use an expensive special optical system for correcting the above-mentioned tilt (a so-called tilt correcting optical system) which has heretofore been required.
However, the inclination of the mounting flange surface of the rotational mirror is generally very small and it is difficult to detect the direction of this inclination. Accordingly, it is also difficult to assemble the rotational mirror with the reflecting surface of the rotational mirror and the direction of inclination of the mounting flange surface being made parallel to each other. Also, even if the direction of inclination is detected at all, there is irregularity during assembly and therefore, it is nearly impossible to assemble a great quantity of rotational mirrors always with good accuracy.
So, in order to reliably achieve a construction in which the reflecting surface of the rotational mirror and the direction of inclination of said mounting flange surface are made parallel to each other, it is an object of the present invention to provide a light deflecting device having structure which can be regulated so that the direction of inclination of the mounting flange surface and the reflecting surface of the rotational mirror may reliably become parallel to each other after the rotational mirror is incorporated into the light deflecting device, and a regulating device therefor.
To achieve the above object, the light deflecting device according to the present invention is of such a construction that by biasing means, the rotational mirror is urged against the mounting surface of a rotational mirror mounting portion rotatable by a rotational mirror driving motor and the rotational mirror can be separated from the mounting surface against the biasing force of the biasing means and when so separated, the rotational mirror and the mounting surface can rotate relative to each other.
Accordingly, after the rotational mirror has been incorporated into the device, the phase relation between the rotational mirror and said mounting surface can be regulated and the rotational mirror can be reliably brought into a state in which the reflecting surface thereof becomes parallel to the direction of inclination of said mounting surface.
In a regulating device in such a light deflecting device, the rotary shaft of the driving motor can be fixed by a clamp portion to thereby fix the mounting surface of the rotational mirror mounting portion and the rotational mirror can be rotated while being floated up from said mounting surface by the pawl of the regulating device, thereby change the phase position thereof.